Natural resources such as gas, oil, and water residing in a geological formation may be recovered by drilling a wellbore into the formation. A string of pipe (e.g., casing) is run into the wellbore in order to provide structural support for the wellbore sides. The casing may be metal (e.g., steel).
Primary cementing may be performed whereby a cement slurry is injected into the annulus between the casing and the geological formation. The cement is permitted to set into a hard mass (i.e., a sheath) to thereby support the string of pipe within the wellbore and seal the annulus. Due to the tightly coupled nature of the formation, sheath, and casing, it may be difficult to evaluate the materials between the pipe and the geological formation.